The present invention generally relates to smart cards, and, more particularly, to a conductive trace design for a smart card.
Referring to FIG. 1A, a smart card 10 having a credit-card sized body 12 with a first major surface 14 that includes an integrated circuit (IC) module receiving area 16 for receiving an IC module 18, and an antenna 20 is shown. FIG. 1B is a top plan view of the IC module 18 before being singulated from a carrier 22. The IC module 18 includes an IC 24, which may be a microcontroller with some memory, mounted on a substrate or lead frame 26, which is a part of the carrier 22. The substrate 26 includes a plurality of vias 28 that allow conductive pads on the active surface of the IC 24 to be electrically connected to contact pads on the opposite side of the substrate 26 with bond wires 30. By including both the antenna 20 and the contact pads, the smart card allows for both contact and contactless connections.
The vias 28 typically comprise plated through holes. One or more conductive traces 32 and 33 are formed on the surface of the substrate 26 and form connections between the IC 24 and the antenna 20. The conductive traces 32 and 33 travel from one via to an adjacent via and so on, as shown in FIG. 1B. The conductive traces 32 and 33 also surround the vias 28, as shown in FIG. 1C, which is a greatly enlarged plan view of the via 28, a bond wire 30 connecting the IC 24 to the via 28, and the conductive trace 32.
Smart card packages have a problem in that sometimes one of the bond wires 30 can sag and inadvertently touch the conductive trace 32, also as shown in FIG. 1C, causing a short circuit condition that may cause the smart card to operate incorrectly. Accordingly, it would be desirable to be able to assembly smart cards that will not have inadvertent short circuits caused by a bond wire inadvertently contacting the conductive trace 32.